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Optics Express

Plasmon-induced multipartite interactions and entanglement in quantum emitter hybrid systems

Peng-tao Du, Guang-ming Huang, Gaoxiang Li, Yaping Yang, Wei Fang

Published Dec 26, 2025• 0 citations

Abstract

This study investigates multipartite entanglement in quantum emitter (QE) systems coupled to a two-dimensional hyperbolic surface (TDHS). Within the master equation framework, which distinguishes the contributions of surface plasmon field (SPF) with different spatial modes, we demonstrate that both the collective decay coefficients and the in-plane emission pattern of the emitters are strongly governed by the polarization of the transition dipole. Numerical analysis further reveals that the TDHS functions as a planar plasmonic waveguide supporting both reciprocal and nonreciprocal inter-emitter interactions. Building on these intriguing properties, we analyze the dynamics of spontaneously generated entanglement (SGE) in tripartite and quadripartite systems under various interaction configurations. Our results show that in certain two-dimensional geometries, strong nonreciprocal interactions enhance global entanglement compared with one-dimensional arrangements. Notably, the rhombic configuration supports destructive interference that suppresses on-site decay and drives the system into dark states with steady entanglement. Moreover, for systems initialized in mixed states, entanglement generation relies mainly on reciprocal interactions and shows only weak dependence on the interaction geometry. These findings provide a versatile route for engineering multipartite entanglement in TDHS-based plasmonic architectures, with promising applications in quantum information processing and integrated photonic devices.

DOI: 10.1364/oe.582555

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We investigate relaxation dynamics in the system of two identical quantum dipole emitters (QDEs) located near a metal nanoparticle (MNP) exhibiting a dipolar localized surface plasmon (LSP) resonance at the frequency of the QDE radiative transition. Considering one QDE to be brought into an optically active excited state and weakly coupled to the resonant LSP, we show that a stable superposition state of two QDEs is formed during the transition time, which is much shorter than the QDE spontaneous decay time and determined by the efficiency of resonant interaction between the QDEs and induced LSP. It is elucidated that the superposition state is established as a result of redistribution of the energy of the initially excited QDE so that the corresponding steady-state QDE fields induced at the MNP site cancel each other. The degree of steady-state entanglement characterized by the concurrence is found dependent only on the ratio of distances between the QDEs and the MNP, reaching its maximum value of $\ensuremath{\sim}0.65$, when the separation between the MNP and the initially excited QDE is larger by $\ensuremath{\sim}20%$ than the distance from the other QDE to the MNP.

We present a combined classical and quantum electrodynamics description of the coupling between two circularly polarized quantum emitters held above a metal surface supporting surface plasmons. Depending on their position and their natural frequency, the emitter-emitter interactions evolve from being reciprocal to nonreciprocal, which makes the system a highly tunable platform for chiral coupling at the nanoscale. By relaxing the stringent material and geometrical constraints for chirality, we explore the interplay between coherent and dissipative coupling mechanisms in the system. Thus, we reveal a quasichiral regime in which its quantum optical properties are governed by its subradiant state, giving rise to extremely sharp spectral features and strong photon correlations.

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Enabling the confinement of light to a scale far below the one of conventional optics, surface plasmon polaritons (SPPs) induced by an electromagnetic field in a metal-dielectric interface supply an ideal system to explore strong quantized light-matter coupling. The fast matter-SPP population exchange reported in previous works makes it a candidate for spin manipulation, but such reversible dynamics asymptotically vanishes accompanying the quantum matter relaxing completely to its ground state. Here, we study the exact dissipative dynamics of a quantum emitter (QE) coupled to SPPs. It is interesting to find that, qualitatively different from conventional findings, the QE can be partially stabilized in its excited state even in the presence of the lossy metal. Our analysis reveals that it is the formation of a QE-SPP bound state which results in such suppressed dissipation. Enriching the decoherence dynamics of the QE in the lossy medium, our result is helpful to understand QE-SPP interactions and apply plasmonic nanostructures in quantum devices.

We theoretically study the dissipative dynamics of a quantum emitter placed near the planar surface of a metal supporting surface-plasmon excitations. The emitter-metal coupling regime can be tuned by varying some control parameters such as the qubit-surface separation and/or the detuning between characteristic frequencies. By using a Green's-function approach jointly with a time-convolutionless master equation, we analyze the non-Markovian dissipative features on the qubit time evolution in two cases of interest: (i) an undriven qubit initially prepared in its excited state and (ii) the evolution toward a steady state for a system driven by a laser field. For weak to moderate qubit-metal coupling strength, and on time scales large compared to the surface plasmon oscillation time, a Markovian approximation for the master-equation results to be adequate to describe the qubit main optical properties: surface enhancements of rate emission, optical spectra, and time-dependent photon-photon correlation functions. The qubit decay shows a crossover passing from being purely dissipative for small qubit-surface distances to plasmon emission for larger separations.

We investigate entanglement mediated by DC current induced nonreciprocal graphene plasmon polaritons. Nonreciprocal systems are ideal for the enhancement, control, and preservation of entanglement due to the potential for unidirectional beam-like wave propagation, i.e., efficiently transporting photons from one emitter to another. Using a quantum master equation and three-dimensional Green's function analysis, we investigate a system consisting of two two-level emitters dominantly interacting via electric current induced nonreciprocal plasmonic modes of a graphene waveguide. We use concurrence as a measure of entanglement. We show that nonreciprocal graphene plasmon polaritons are a promising candidate to generate and mediate concurrence, where it is shown that there is good enhancement and control of entanglement over vacuum, which is beneficial for the broad applications of entanglement as a quantum resource. We believe our findings contribute to the development of quantum devices, enabling efficient and tunable entanglement between two-level systems, which is a central goal in quantum technologies.